First thing you need to do is review the permissions for the folder in question. Secondly, to view all of the extra data for the appointment, open the appointment, and then go to Tools-->Forms-->Design this form. Click the All Fields tab. Use the "Select from" drop-down list to view the various hidden fields. The Mail fields may give you an indication of who last sent an appointment change. I haven't found a "Modified by" field, but a VBA wiz may be able to tell us if such a field is accessible.
